Browsing by Author "Steenkamp, Emma T."

Now showing 1 - 7 of 7
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    Genome sequences of Knoxdaviesia capensis and K. proteae (Fungi: Ascomycota) from Protea trees in South Africa
    (BioMed Central, 2016) Aylward, Janneke; Steenkamp, Emma T.; Dreyer, Leanne L.; Roets, Francois; Wingfield, Brenda D.; Wingfield, Michael J.
    Two closely related ophiostomatoid fungi, Knoxdaviesia capensis and K. proteae, inhabit the fruiting structures of certain Protea species indigenous to southern Africa. Although K. capensis occurs in several Protea hosts, K. proteae is confined to P. repens. In this study, the genomes of K. capensis CBS139037 and K. proteae CBS140089 are determined. The genome of K. capensis consists of 35,537,816 bp assembled into 29 scaffolds and 7940 predicted protein-coding genes of which 6192 (77.98 %) could be functionally classified. K. proteae has a similar genome size of 35,489,142 bp that is comprised of 133 scaffolds. A total of 8173 protein-coding genes were predicted for K. proteae and 6093 (74.55 %) of these have functional annotations. The GC-content of both genomes is 52.8 %.
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    Identification of the gene for β-fructofuranosidase from Ceratocystis moniliformis CMW 10134 and characterization of the enzyme expressed in Saccharomyces cerevisiae
    (BioMed Central, 2013-11) Van Wyk, Niel; Trollope, Kim M.; Steenkamp, Emma T.; Wingfield, Brenda D.; Volschenk, Heinrich
    Background: β-Fructofuranosidases (or invertases) catalyse the commercially-important biotransformation of sucrose into short-chain fructooligosaccharides with wide-scale application as a prebiotic in the functional foods and pharmaceutical industries. Results: We identified a β-fructofuranosidase gene (CmINV) from a Ceratocystis moniliformis genome sequence using protein homology and phylogenetic analysis. The predicted 615 amino acid protein, CmINV, grouped with an existing clade within the glycoside hydrolase (GH) family 32 and showed typical conserved motifs of this enzyme family. Heterologous expression of the CmINV gene in Saccharomyces cerevisiae BY4742Δsuc2 provided further evidence that CmINV indeed functions as a β-fructofuranosidase. Firstly, expression of the CmINV gene complemented the inability of the Δsuc2 deletion mutant strain of S. cerevisiae to grow on sucrose as sole carbohydrate source. Secondly, the recombinant protein was capable of producing short-chain fructooligosaccharides (scFOS) when incubated in the presence of 10% sucrose. Purified deglycosylated CmINV protein showed a molecular weight of ca. 66 kDa and a Km and Vmax on sucrose of 7.50 mM and 986 μmol/min/mg protein, respectively. Its optimal pH and temperature conditions were determined to be 6.0 and 62.5°C, respectively. The addition of 50 mM LiCl led to a 186% increase in CmINV activity. Another striking feature was the relatively high volumetric production of this protein in S. cerevisiae as one mL of supernatant was calculated to contain 197 ± 6 International Units of enzyme. Conclusion: The properties of the CmINV enzyme make it an attractive alternative to other invertases being used in industry.
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    Knoxdaviesia proteae is not the only Knoxdaviesia-symbiont of Protea repens
    (International Mycological Association, 2015-11-10) Aylward, Janneke; Dreyer, Leanne L.; Steenkamp, Emma T.; Wingfield, Michael J.; Roets, Francois
    Two polyphyletic genera of ophiostomatoid fungi are symbionts of Proteaceae in southern Africa. One of these, Knoxdaviesia, includes two closely related species, K. proteae and K. capensis, that have overlapping geographical distributions, but are not known to share Protea host species. Knoxdaviesia capensis appears to be a generalist that occupies numerous hosts, but has never been found in P. repens, the only known host of K. proteae. In this study, extensive collections were made from P. repens and isolates were identified using DNA sequence comparisons. This led to the surprising discovery of K. capensis from P. repens for the first time. The fungus was encountered at a low frequency, suggesting that P. repens is not its preferred host, which may explain why it has not previously been found on this plant. The basis for the specialisation of K. proteae and K. capensis on different Protea species remains unknown.
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    Nine draft genome sequences of Claviceps purpurea s.lat., including C. arundinis, C. humidiphila, and C. cf. spartinae, pseudomolecules for the pitch canker pathogen Fusarium circinatum, draft genome of Davidsoniella eucalypti, Grosmannia galeiformis, Quambalaria eucalypti, and Teratosphaeria destructans
    (International Mycological Association, 2018-12-01) Wingfield, Brenda D.; Liu, Miao; Nguyen, Hai D. T.; Lane, Frances A.; Morgan, Seamus W.; De Vos, Lieschen; Wilken, P. M.; Duong, Tuan A.; Aylward, Janneke; Coetzee, Martin P. A.; Dadej, Kasia; De Beer, Z. W.; Findlay, Wendy; Havenga, Minette; Kolarik, Miroslav; Menzies, Jim G.; Naidoo, Kershney; Pochopski, Olivia; Shoukouhi, Parivash; Santana, Quentin C.; Seifert, Keith A.; Soal, Nicole; Steenkamp, Emma T.; Tatham, Catherine T.; Van Der Nest, Margriet A.; Wingfield, Michael J.
    This genome announcement includes draft genomes from Claviceps purpurea s.lat., including C. arundinis, C. humidiphila and C. cf. spartinae. The draft genomes of Davidsoniella eucalypti, Quambalaria eucalypti and Teratosphaeria destructans, all three important eucalyptus pathogens, are presented. The insect associate Grosmannia galeiformis is also described. The pine pathogen genome of Fusarium circinatum has been assembled into pseudomolecules, based on additional sequence data and by harnessing the known synteny within the Fusarium fujikuroi species complex. This new assembly of the F. circinatum genome provides 12 pseudomolecules that correspond to the haploid chromosome number of F. circinatum. These are comparable to other chromosomal assemblies within the FFSC and will enable more robust genomic comparisons within this species complex.
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    Panmixia defines the genetic diversity of a unique arthropod-dispersed fungus specific to Protea flowers
    (Wiley Open Access, 2014-09) Aylward, Janneke; Dreyer, Leanne L.; Steenkamp, Emma T.; Wingfield, Michael J.; Roets, Francois
    Knoxdaviesia proteae, a fungus specific to the floral structures of the iconic Cape Floral Kingdom plant, Protea repens, is dispersed by mites phoretic on beetles that pollinate these flowers. Although the vectors of K. proteae have been identified, little is known regarding its patterns of distribution. Seed bearing infructescences of P. repens were sampled from current and previous flowering seasons, from which K. proteae individuals were isolated and cultured. The genotypes of K. proteae isolates were determined using 12 microsatellite markers specific to this species. Genetic diversity indices showed a high level of similarity between K. proteae isolates from the two different infructescence age classes. The heterozygosity of the population was high (0.74 +- 0.04), and exceptional genotypic diversity was encountered (^G = 97.87%). Population differentiation was negligible, owing to the numerous migrants between the infructescence age classes (Nm = 47.83) and between P. repens trees (Nm = 2.96). Parsimony analysis revealed interconnected genotypes, indicative of recombination and homoplasies, and the index of linkage disequilibrium confirmed that outcrossing is prevalent in K. proteae (rd = 0.0067; P = 0.132). The high diversity and panmixia in this population is likely a result of regular gene flow and an outcrossing reproductive strategy. The lack of genetic cohesion between individuals from a single P. repens tree suggests that K. proteae dispersal does not primarily occur over short distances via mites as hypothesized, but rather that longdistance dispersal by beetles plays an important part in the biology of these intriguing fungi.
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    A plant pathology perspective of fungal genome sequencing
    (International Mycological Association, 2017) Aylward, Janneke; Steenkamp, Emma T.; Dreyer, Leanne L.; Roets, Francois; Wingfield, Brenda D.; Wingfield, Michael J.
    The majority of plant pathogens are fungi and many of these adversely affect food security. This minireview aims to provide an analysis of the plant pathogenic fungi for which genome sequences are publically available, to assess their general genome characteristics, and to consider how genomics has impacted plant pathology. A list of sequenced fungal species was assembled, the taxonomy of all species verified, and the potential reason for sequencing each of the species considered. The genomes of 1090 fungal species are currently (October 2016) in the public domain and this number is rapidly rising. Pathogenic species comprised the largest category (35.5 %) and, amongst these, plant pathogens are predominant. Of the 191 plant pathogenic fungal species with available genomes, 61.3 % cause diseases on food crops, more than half of which are staple crops. The genomes of plant pathogens are slightly larger than those of other fungal species sequenced to date and they contain fewer coding sequences in relation to their genome size. Both of these factors can be attributed to the expansion of repeat elements. Sequenced genomes of plant pathogens provide blueprints from which potential virulence factors were identified and from which genes associated with different pathogenic strategies could be predicted. Genome sequences have also made it possible to evaluate adaptability of pathogen genomes and genomic regions that experience selection pressures. Some genomic patterns, however, remain poorly understood and plant pathogen genomes alone are not sufficient to unravel complex pathogen-host interactions. Genomes, therefore, cannot replace experimental studies that can be complex and tedious. Ultimately, the most promising application lies in using fungal plant pathogen genomics to inform disease management and risk assessment strategies. This will ultimately minimize the risks of future disease outbreaks and assist in preparation for emerging pathogen outbreaks.
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    Roots and nodules response differently to P starvation in the mediterranean-type legume virgilia divaricata
    (Frontiers Media, 2019-02-05) Stevens, Gary G.; Perez-Fernandez, Maria A.; Morcillo, Rafael J. L.; Kleinert, Aleysia; Hills, Paul; Brand, D. Jacobus; Steenkamp, Emma T.; Valentine, Alex J.; Garcia-Mina, Jose M.
    ENGLISH ABSTRACT: Virgilia divaricata is a tree legume that grows in the Cape Floristic Region (CFA) in poor nutrient soils. A comparison between high and low phosphate growth conditions between roots and nodules was conducted and evaluated for the plants ability to cope under low phosphate stress conditions in V. divaricata. We proved that the plant copes with low phosphate stress through an increased allocation of resources, reliance on BNF and enhanced enzyme activity, especially PEPC. Nodules had a lower percentage decline in P compared to roots to uphold its metabolic functions. These strategies partly explain how V. divaricata can sustain growth despite LP conditions. Although the number of nodules declined with LP, their biomass remained unchanged in spite of a plant decline in dry weight. This is achieved via the high efficiency of BNF under P stress. During LP, nodules had a lower % decline at 34% compared to the roots at 88%. We attribute this behavior to P conservation strategies in LP nodules that imply an increase in a metabolic bypass that operates at the PEP branch point in glycolysis. The enhanced activities of nodule PEPC, MDH, and ME, whilst PK declines, suggests that under LP conditions an adenylate bypass was in operation either to synthesize more organic acids or to mediate pyruvate via a non-adenylate requiring metabolic route. Both possibilities represent a P-stress adaptation route and this is the first report of its kind for legume trees that are indigenous to low P, acid soils. Although BNF declined by a small percentage during LP, this P conservation was evident in the unchanged BNF efficiency per weight, and the increase in BNF efficiency per mol of P. It appears that legumes that are indigenous to acid soils, may be able to continue their reliance on BNF via increased allocation to nodules and also due to increase their efficiency for BNF on a P basis, owing to P-saving mechanisms such as the organic acid routes.